In the processing of web-shaped goods, a basic differentiation is typically made between folding apparatuses with spur needle cylinder or folding apparatuses with gripper cylinders. The folding apparatus is constructed in the appropriate configuration as a function of customer requests and/or as a function of the product to be formed. Based on properties, in connection with the use of gripper cylinders, as will be discussed subsequently, considerable differences arise, as a rule, in the formation of the same size product. Such differences result, for example, in the cylinder size, in the position of the cylinders with respect to each other and therefore in the embodiment of the frame, the drive geometry of the drive train, and many others. In connection with the construction of a folding apparatus, these differences have required, up to the present, a restriction to a type of folding apparatus, as well as to dual construction of the same folding apparatus format of both types.
A spur needle cylinder has spur needles, and in particular has retractable spur needles on its circumference, which spur needles pick up the continuous web, which web, following further conveyance, is transversely cut into sections. The next following section is then grasped by the subsequent spur needles which are following on the circumference of the spur needle cylinder, and is cut in the same way. No spacing is required between the web sections following each other on the circumference of the spur needle cylinder, so that the spur needle cylinder can have the same circumferential velocity as the conveying speed of the continuous web. Spur needle cylinders and subsequent cylinders, such as, for example, folding jaw cylinderscan have the same circumference.
A gripper cylinder has one or several grippers on its shell face, which grippers are movable between a gripping or clamping position, in which they maintain a leading end of a flat material, which is to be conveyed on the gripper cylinder, pressed against the shell face, and a release position in which the flat material can again be detached from the cylinder, or in which a new piece of flat material can be picked up and clamped. The grippers generally perform a pivot movement between these two positions. Since the amounts of time available for either clamping or for releasing a product are short, the pivot movement must be done at a high speed. A movement amplitude between the clamping position and the release position of the gripper should be as short as possible in order to keep accelerations, which stress the material, within limits.
To prevent the infliction of damage, by a gripper, to a trailing end of a piece of flat material which is maintained on the cylinder, because of the movement of a gripper which follows the piece of flat material on the cylinder in the circumferential direction, in the course of clamping a following piece of flat material, most gripper cylinders are configured to receive pieces of flat material which are supplied to the gripper cylinder separated from each other. The pieces of flat material thus each come to rest on the gripper cylinder, while forming a gap between successive ones of the pieces. The gripper can move in the resulting gap without touching the previous piece of material. If these pieces of flat material had previously been produced by being cut off a continuous web, it is necessary, in order to form such a gap, to accelerate the cut-off pieces to a speed which is greater than that of the continuous web prior to cutting of the web. However, if a conveying system, which conveys the products cut off the continuous web, runs faster than the conveyed continuous web after the pieces have been cut from the conveyed continuous web, this leads to slippage and therefore to friction between the conveying system and a leading section of the continuous web entering it, which leading section of the web necessarily still moves at the original speed of the continuous web prior to their cut-off. In the case of flat material with a sensitive surface, such as, for example, freshly printed products, this friction can negatively affect the quality of the surface, for example by the production of drag marks on the imprinted material, or by smearing of the ink. If the pieces of flat material are composed of a stack of sheets, which sheets are not connected with each other, the problem furthermore occurs that different friction at different sides of the stack can lead to the sheets being displaced with respect to each other. This can lead to the stack being pulled apart, which stack separation makes further use of the stack considerably more difficult.
It is particularly problematical if the pieces of flat material are being cut off the continuous web while they are directly in contact with the gripper cylinder, such as, for example, by the use of a rotating cutter cylinder which, together with the gripper cylinder, defines a cutting gap and which cutter cylinder severs the continuous web in cooperation with a thrust element of the gripper cylinder. To insure that the continuous web which is to be cut rests evenly against the surface of the gripper cylinder, the grippers must be capable of dipping or retracting into the interior of the gripper cylinder. After a piece of flat material has been cut off the continuous web, there is very little time which is available to grasp the newly created leading edge of the continuous web, by the use of a gripper, and to press this newly created leading edge against the surface of the cylinder. However, the path between the retracted position of the gripper and the extended position of the gripper, in which extended position the flat piece of material is pressed against the cylinder, is long and thus requires a high speed of the gripper movement. Such high speed can only be realized with the use of a high-quality, expensive drive mechanism. Moreover, wear, and therefore the susceptibility of the drive mechanism to breakdowns, is all the greater, the higher its operating speed is.
A gripper cylinder is known from EP 0 931 748 B1. This device is capable of conveying printed products which have been cut off a supplied continuous web without precession, i.e. without a space between the printed products following each other. With this gripper cylinder, a gripper is mounted on a shaft, which shaft is pivotably seated in the cylinder and by the use of a translatory mechanism which, when coupled to the pivot movement, drives the gripper to perform a parallel displacement. This translatory mechanism is used to displace the gripper between its retracted position and a position where it projects past the shell face of the cylinder, from which projected position it can be pivoted around the shaft to press the leading edge of a continuous web of printed products against the cylinder surface.
The construction of the translatory mechanism, nor how the movement of the translatory mechanism is to be driven are not specifically described. A mechanical coupling of the translatory mechanism to the rotation of the gripper cylinder would require extensive gearing. Although it is conceivable to provide an electrical or a hydraulic drive unit for the displacement, which drive unit pivots around the shaft, together with the gripper, the problem of supplying the necessary drive energy arises. Furthermore, such a drive unit would considerably increase the moment of inertia of the gripper to be pivoted and would therefore reduce the speed of movement of the gripper which could be reached.
A folding apparatus, which is configured without spur needles, and with a gripper cylinder is known from DE 42 29 059 A1, and in whose surface speed is precessed over the speed of the continuous web.
DE 197 16 625 A1 shows a folding apparatus with a spur needle cylinder. The spur needle cylinder, the cutter cylinder and the pre-folding cylinder are seated in a common frame.